btrfs: allow idmapped SUBVOL_SETFLAGS ioctl

Setting flags on subvolumes or snapshots are core features of btrfs. The
SUBVOL_SETFLAGS ioctl is especially important as it allows to make
subvolumes and snapshots read-only or read-write. Allow setting flags on
btrfs subvolumes and snapshots on idmapped mounts. This is a fairly
straightforward operation since all the permission checking helpers are
already capable of handling idmapped mounts. So we just need to pass
down the mount's userns.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index aa60a957874799f52bbea44eb09bafed3c678b9d..9d54149bad6ecbd77aeb7bafb70075500970435a 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1988,7 +1988,7 @@ static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
        u64 flags;
        int ret = 0;
 
-       if (!inode_owner_or_capable(&init_user_ns, inode))
+       if (!inode_owner_or_capable(file_mnt_user_ns(file), inode))
                return -EPERM;
 
        ret = mnt_want_write_file(file);